The present invention is related generally to electronic devices whose functional length scales are measured in nanometers, and, more particularly, to a latch for use with crossbar arrays based on crossed nanometer-scale wires joined by voltage-settable switches at the intersecting junctions.
Nano-computing is based on the premise of switches that are of nanometer scale in the functional dimension(s). Examples of technology used in implementing nano-scale switches are disclosed and claimed in the following: application Ser. No. 09/282,048, entitled xe2x80x9cChemically Synthesized and Assembled Electronic Devicesxe2x80x9d, filed on Mar. 29, 1999, in the names of James R. Heath et al; application Ser. No. 09/280,225, entitled xe2x80x9cMolecular Wire Crossbar Interconnectxe2x80x9d, filed on Mar. 29, 1999, in the names of Philip J. Kuekes et al; application Ser. No. 09/282,045, entitled xe2x80x9cMolecular Wire Crossbar Logic (MWCL)xe2x80x9d, filed on Mar. 29, 1999, in the names of Philip J. Kuekes et al; U.S. Pat. No. 6,128,214, entitled xe2x80x9cMolecular Wire Crossbar Memoryxe2x80x9d, issued to Philip J. Kuekes et al on Oct. 3, 2000; and U.S. Pat. No. 6,256,767, entitled xe2x80x9cDemultiplexer for a Molecular Wire Crossbar Networkxe2x80x9d, issued to Philip J. Kuekes et al on Jul. 3, 2001, all assigned to the same assignee as the present application.
To have fully general computing, one must have not only logic functions and memory functions, but we must be able to take a logical variable and put it into a memory and be able to reuse it as the input to another logic function. This al lows one to build finite state machines and thus do completely general computing. One method of doing this is to use a latch.
While such a latch is well-known in the art of general computing, as that art has developed in the year 2001, advances in the art of nano-computing require new approaches to developing a latching functionality at the nanometer scale.
Thus, what is needed is a latch that is specifically configured for nano-meter-scale computing and is compatible in size with nanometer scale logic.
In accordance with the present invention, a molecular crossbar latch is provided, comprising two control wires and a signal wire that crosses the two control wires at a non-zero angle to thereby form a junction with each control wire. Each junction forms a switch and the junction has a functional dimension in nanometers. The signal wire selectively has at least two different voltage states, ranging from a 0 state to a 1 state, wherein there is an asymmetry with respect to the direction of current flow from the signal wire through one junction compared to another junction such that current flowing through one junction into (out of) the signal wire can open (close) the first switch while current flowing through the other junction out of (into) the signal wire can close (open) the other switch, and wherein there is a voltage threshold for switching between an open switch and a closed switch.
A method is provided for latching logic values onto nanowires in a logic method comprises:
(a) providing the molecular crossbar latch; and
(b) applying a sequence of voltages to the two control wires that results in setting the switches of the two junctions such that either the first switch is open and the second switch is closed if the signal wire had a voltage representing a logic 1, or the first switch is closed and the second switch is open if the signal wire had a voltage age representing a logic 0, thereby latching the signal.
Secondly, a method is provided for restoring a voltage value of a signal in a nano-scale switch. The method comprises:
(a) providing the molecular crossbar latch;
(b) latching the signal as above; and
(c) placing a voltage representing logic 0 on the first control wire and a voltage representing logic 1 on the second control wire.
Finally, a method is provided for inverting a voltage value of a signal in a nano-scale switch. The method comprises:
(a) providing the molecular crossbar latch;
(b) latching the signal as above; and
(c) placing a voltage representing logic 1 on the first control wire and a voltage representing logic 0 on the second control wire.
No latch has previously been demonstrated at the nanometer scale. The present invention allows a nanometer scale latch to be both constructed and integrated with other circuits using the crossbar. Further, the present invention provides at a nanometer scale: latching of an arbitrary logic signal, restoration of logic signal strength, possible inversion of the latched output, and multiple latches with very few clocking connections to outside circuits. The combination of the proceeding features allows the construction of arbitrarily complex logic designs.